@incollection{Wirsching1998a,
  author    = {{Günther J. Wirsching}},
  title     = {{The Dynamical System Generated by the $3n + 1$ Function}},
  booktitle = {{Lecture Notes in Math. No. 1681}},
  publisher = {{Springer-Verlag: Berlin}},
  year      = {{1998}},
  note      = {{MR 99g:11027}},
}